function y = k_tail(e)
    
    Ts = 4; g = 3/2; p = 5/3;

    alpha_s1 = 1 / ( (p-1)*Ts*2^(p/2-3/2) );
    beta_s1  = g / ( (g-1)*Ts*2^(1/(2*g)-3/2));

    y = g * alpha_s1 * (p-1/g) * ( ( alpha_s1 * abs(e) ^ (p-1/g) + beta_s1 ) ^ (g-1) ) * abs(e) ^ (p-1/g);

end